The buildup did not result in any “safety related consequences” or injuries, but the NRC said “the potential for such consequences may have existed.’’

Records indicate the amount of uranium exceeded a limit of 29 kilograms.

While the NRC investigation is ongoing, the plant’s operator, Westinghouse, voluntarily shut down part of the facility and began notifying some employees of a “temporary workforce reduction,’’ said company spokeswoman Courtney Boone.

Boone said 170 of the company’s 1,000 employees in Columbia fell victim to the job reduction.

Boone said affected employees are being offered no-interest loans while they are out of work. Medical benefits will be covered during the workforce reduction, she said. The force reduction is not because of safety concerns, she said.

The Westingthouse plant, located between Interstate 77 and Congaree National Park, makes nuclear fuel for atomic power plants around the country.

The plant is a mainstay of the Columbia-area economy and often gets high marks from supporters. But the NRC also has hit Westinghouse with about a dozen enforcement actions in South Carolina during the past 20 years, most recently in 2011, records show.

In this case, NRC officials, who learned recently of the uranium buildup from Westinghouse officials, say an air scrubber at the plant contained “an unexpectedly large amount of material’’ inside. The agency characterized the amount as “excessive.’’

Once they analyzed the material, federal officials found it contained uranium levels higher than allowed under NRC requirements.

Scrubbers are pollution control devices designed to prevent contaminants from getting into the environment. The area where the uranium buildup occurred supports a process of converting uranium hexafluoride into uranium dioxide powder, before being turned into pellets for commercial nuclear fuel rods.

NRC spokesman Roger Hannah said nuclear materials can cause an atomic reaction if not handled carefully, which is why the agency is taking the matter seriously.